(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of using laser annealing to form a high quality titanium silicide in the fabrication of integrated circuits.
(2) Description of the Prior Art
Due to the xe2x80x9cfine line effect,xe2x80x9d C54 titanium disilicide is difficult to achieve in sub 0.18 xcexcm polysilicon lines. Typically, a C49 phase titanium disilicide (TiSi2) is formed after a first annealing. This material has a high resistivity however, so a second annealing is performed to change the phase of the TiSi2 to C54, which has much lower resistivity. An additional silicon implantation step has been used for salicidation, to change the top portion of the silicon substrate to an amorphous layer, but this causes transient enhanced dopant diffusion, dopant redistribution, silicon defects, and, hence, device degradation. It is desired to find a method to form a high quality C54 TiSi2 that can be achieved for deep submicron feature sizes.
A number of patents teach formation of C54 titanium silicide. U.S. Pat. No. 5,937,325 to Ishida teaches using laser annealing to form C49 TiSi2, then a rapid thermal annealing (RTA) to form C54 TiSi2 on a polysilicon gate. Then, a first and second RTA form C49, then C54 TiSi2 on the source/drain regions. U.S. Pat. No. 6,054,387 to Fukuda teaches forming C49 TiSi2 by RTA, then warping the device while performing a second RTA to form C54 TiSi2. U.S. Pat. No. 6,071,552 to Ku discloses deposition of C49 TiSi2, then an RTA to form C54 TiSi2. U.S. Pat. No. 5,956,137 to Lim et al discloses a method to use Raman analysis to determine the phase of a silicide.
A principal object of the present invention is to provide an effective and very manufacturable method of fabricating a titanium disilicide film in the fabrication of an integrated circuit.
A further object of the invention is to provide a method of fabricating C54 phase titanium disilicide in the fabrication of an integrated circuit.
Yet another object is to provide a method of forming a C54 phase titanium disilicide film for deep submicron devices.
Yet another object is to provide a method of forming a C54 phase titanium disilicide film for deep submicron devices wherein the C54 phase is formed based on a C40 titanium disilicide.
Yet another object of the invention is to forming a C54 phase titanium disilicide film using laser annealing to first form C40 phase titanium disilicide, and then using a lower temperature annealing to form C54 phase titanium disilicide.
In accordance with the objects of the invention a novel method for forming a C54 phase titanium disilicide film in the fabrication of an integrated circuit is achieved. A semiconductor substrate is provided having silicon regions to be silicided. A titanium layer is deposited overlying the silicon regions to be silicided. The substrate is subjected to a first annealing whereby the titanium is transformed to phase C40 titanium disilicide where it overlies the silicon regions and wherein the titanium not overlying the silicon regions is unreacted. The unreacted titanium layer is removed. The substrate is subjected to a relatively low temperature second annealing whereby the phase C40 titanium disilicide is transformed to phase C54 titanium disilicide to complete formation of a phase C54 titanium disilicide film in the manufacture of an integrated circuit.